1. Field of the Invention
The present invention relates generally to battery operated vehicles, and more particularly to methods and systems for controlling vehicle battery temperature.
2. Background Art
Hybrid electric vehicles or pure electric vehicles typically include a high voltage battery to provide power for driving the vehicle. The performance of the vehicle and the service life of the battery can be affected by extreme temperature conditions.
Batteries tend to provide less discharge power and accept less charge when cold. This is a problem as it can reduce the benefit of using the battery and lead to inconsistent performance in cold weather conditions.
As discussed in U.S. Pat. No. 6,163,135, the charging and discharging of the battery during vehicle operation causes its internal resistances to heat the battery. One shortcoming of the design disclosed in the patent, however, is its inability to heat the battery when the vehicle is shut-off. This shortcoming is particularly disadvantageous as the battery can experience excessive cooling when shut-off.
A battery heater can be used during vehicle shut-off to heat the battery. The battery heater is typically a vehicle mounted component, which includes a cord or other electrical connector to connect the heater to a wall outlet or other remote source of electric energy. The disadvantage of such heaters is that a user is required to plug in the heater. Plugging in the heater, if a wall outlet or other remote source of electric energy is available, is inconvenient.
Accordingly, it would be desirable to provide a more convenient battery heater.